The fabrication of modern integrated circuits typically involves several steps. Integrated circuits are first fabricated on a semiconductor wafer, which contains multiple duplicated semiconductor chips, each comprising integrated circuits therein. The semiconductor chips are then sawed from the wafer and packaged. The packaging processes have two main purposes: to protect delicate semiconductor chips, and to connect interior integrated circuits to exterior pins.
In conventional packaging processes, a semiconductor chip may be mounted on a package component using flip-chip bonding. An Underfill is dispensed into the gap between the semiconductor chip and the package component to prevent cracks from being formed in solder bumps or solder balls, wherein cracks are typically caused by thermal stresses. The package component may be an interposer that includes metal connections for routing electrical signals between opposite sides. The chip may be bonded to the interposer through direct metal bonding, solder bonding, or the like.
With the increasing demand for more functions, package-on-package (PoP) technology is used to further expand the integration ability of the packages. When the PoP technology is used, packages are stacked. There are various designs regarding how the PoP structures can be formed. By using the PoP technology, the package design becomes more flexible and less complex. Time-to-market is also reduced for product upgrades. With a high degree of integration, the electrical performance of the resulting package is also improved due to the shortened connecting paths between the package components.